Encapsulation of active material, such as fragrances, is well known in the art. Encapsulation provides advantages to the fragrance product including the protection of the fragrance in the capsule core by a shell until the fragrance is intended to be delivered. In particular, capsules are often designed to deliver their contents at a desired time by the capsule shell being compromised at the desired time.
The capsule shell can be compromised by various factors such as temperature so that the contents are delivered when the capsule begins to melt. Alternatively the capsules can be compromised by physical forces, such as crushing, or other methods that compromise the integrity of the capsule. Additionally, the capsule contents may be delivered via diffusion through the capsule wall during a desired time interval.
It is obviously not desired that the core be released from the shell prematurely. Often, the capsule shell is somewhat permeable to the core contents when stored under certain conditions. This is particularly the case when many capsule types, such as those having aminoplast or cross-linked gelatin walls, are stored in aqueous bases, particularly those containing surfactants. In these cases, although the capsule shell is intact, the fragrance is removed from the core over time in a leaching process. The overall leaching mechanism may be viewed as a diffusion process, with transfer occurring from the capsule core to the aqueous media, followed by transfer to or solubilization into the surfactant micelles or vesicles. With normal surfactant concentrations of between 4 and 30% in consumer products, as compared to fragrance levels of 0.3 to 1%, it is clear that the partitioning favors absorption by the surfactant over time.
In order to enhance the effectiveness of the fragrance material for the user, various technologies such as the encapsulation of the fragrance material in a polymeric protective coating have been employed to enhance the delivery of the fragrance material at the desired time. The polymeric material is used to protect the fragrance material from evaporation, reaction, oxidation or otherwise dissipating prior to use.
While encapsulation of fragrance in a polymeric shell can help prevent fragrance degradation and loss, it is often not sufficient to significantly improve fragrance performance in consumer products. In view of the existing technology, there is an ongoing need to develop fragrance systems which are designed to retain the fragrance with minimal losses until it is needed and then be able to deliver the fragrance at the appropriate time.
The use of nanoscaled material has been recently reported for pharmaceutical application. The main method of encapsulation has been limited to the physical blending of nanoscaled emulsions with active ingredients and the processing afterwards either by freeze, spray or fluidized bed drying process. There are several deficiencies of the process. The active ingredient has generally been limited to solids and the loading of the system is very low. Because of the process involved, the nanostructure of the material is not ensured in the final product. Additionally, a matrix based system will have limited use in applications such as fragrance delivery where robust stability is needed. Polymer systems have been researched and commercialized as fragrance and flavor delivery systems to facilitate application and for better performance, however the delivery system employed is either a polymer matrix or capsule. The use of the nanoscaled material as part of the fragrance core material in fragrance capsules has not been disclosed. The benefits of produced capsules with controlled physical dimensions and consumer benefits of such encapsulated systems have not been discussed before. This may be due to the technical challenges of creating a true nanodispered system for such applications and the difficulties in creating a true core/shell structure involving this type of material.
The use of micro-sized and nanoscaled titanium dioxide and zinc oxide in personal care product have been documented. Both oxides have been incorporated into sunscreen product to protect the skin from harmful UV radiations. The material is often emulsified into person care cream or gel. The use of encapsulated titantium dioxide or zinc oxides in rinse off products has not been disclosed. As a delivery system, these oxides have not been used directly in consumer products such as rinse conditioner because of their hydrophobic properties.
We have now discovered that nanoscaled material can be encapsulated in combination with active material to obtain capsules containing active and nanoscaled material. The fragrance capsules containing nanoscaled material have unique physical and application properties and superior performance can be obtained by such encapsulates. The delivery system can be used in a range of consumer and personal care applications including rinse conditioner, detergent, cleaners, personal care, hair care, sun screen formulation, liquid makeup, and textile.